The present invention relates generally to a GaAs-InGaAs high electron mobility transistor, and more particularly to a .delta.-doping GaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor.
To date, most reports have concentrated on the AlGaAs/InGaAs modulation-doped high electron mobility transistors(HEMT) with better element property whose pseudomorphic structure that are grown by Molecular Beam Epitaxy (MBE) technique. The main reasons are: better bandgap discontinuity, channel mobility and saturation velocity result in higher 2-dimensional electron gas concentration than GaAs/InGaAs MOSFET. However, this prior art has following drawbacks: (1) In Al.sub.x Ga.sub.1-x As, when x content is more than 0.2, the defects occur (i.e. DX centers). (2) The molecular-beam epitaxy (MBE) method cannot grow in mass production, while the metal organic chemical vapor deposition (MOCVD) method can produce massively but cannot produce high quality AlGaAs epilayer. (3) Although its transconductance is high, its gate operating voltage is always confined within or less than 1 volts, and therefore cannot be used effectively in linear amplification.
The drawbacks mentioned above limit the practical applications of pseudomorphic AlGaAs/InGaAs transistors.